resent analyses showed that after the deposition of Lm332, the c2 short arm and the a3 LG4-5 domain were released by proteolytic cleavage. This suggests that they are PHA-793887 supplier required for the Lm332 deposition but not directly involved in the polymerization. It is expected that the interaction of the c2 short arm with heparan sulfate proteoglycans or sulfated glycolipids plays a critical role in the efficient deposition of Lm332. Our results that Lm511 and Lm311 were not deposited on the matrix also imply the important role of the laminin c2 short arm in the Lm332 deposition. Further studies are required to clarify how the cleaved Lm332 selfpolymerizes in the matrix. Although there were numerous studies on the biological activity of Lm332 protein, few reports compared the activities of Lm332ECM and purified Lm332. Here we demonstrated that Lm332ECM was clearly different from the purified, coated Lm332 substrate concerning the biological activity. It has been accepted that purified Lm332 efficiently supports cell adhesion and migration. However, Lm332-ECM supported the adhesion of keratinocytes much more rapidly and strongly than the purified 10 Characterization of Polymerized Laminin-332 Matrix integrin a64 contributed to the cell adhesion to Lm332-ECM more greatly than that to purified Lm332. The interaction of Lm332 with the cell surface integrin a64 nucleates the stable cell adhesion structure hemidesmosome in keratinocytes. The present immunocytochemical staining with an anti-integrin 4 antibody revealed numerous detergent-resistant, hemidesmosomelike structures in the cells adhered to Lm332-ECM, whereas these structures 
were almost absent in the cells adhered to purified Lm332. Based on all these data, it may be concluded that the polymerized Lm332 matrix strongly binds to integrins a31 and a64, and the latter binding promotes hemidesmosome formation, resulting in the tight and stable cell adhesion and the suppressed cell migration. Our finding is similar to the previous study that three-dimensionally organized fibronectin matrix has stronger cell adhesion activity than purified fibronectin. The stable adhesion of keratinocytes to Lm332-ECM mimics the interaction of Lm332 with integrin a64 in the hemidesmosome structure of basal keratinocytes in vivo. Lm332 is known to bind to type VII collagen via the short arm of the 3 chain, forming the anchoring filaments. It is highly expected that the self-polymerization of Lm332 occurs in normal basement membranes and type VII collagen binds to the polymerized Lm332. These Lm332-dependent cell structures could support the stable anchoring of the edpidermis to the dermis in the normal skin. On the other hand, the cell motility activity of Lm332 is thought to contribute to wound repair and tumor invasion. We have previously reported PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22189542 that Lm332 stimulates cell migration in a soluble form. It has been reported that matrix metalloproteinases capable of cleaving the short arm of the laminin c2 chain are overexpressed in pathological conditions such as wound healing and cancer invasion. It is expected that the proteolytic cleavage of the c2 chain prevents the polymerization and assembly of Lm332 into the basement membrane. The resultant soluble Lm332, like coated Lm332, is likely to promote the migration of normal skin cells and cancer cells in the wound healing and cancer invasion, respectively. In conclusion, the present study strongly suggests that the contrasting activities of Lm332, i.e. the stable cel
